Aquarium Ozonizers: Creating Healthy Water Conditions

by Aquatics on April 21, 2010

Written by Mike S. who works in Drs. Foster and Smith’s Technical Support Department.

AquaZone Deluxe Ozonizer

AquaZone Deluxe Ozonizer

When used correctly, an aquarium ozonizer can prove to be extremely useful in creating healthy water conditions for the livestock in an aquarium. Ozonizers can be utilized in marine aquarium setups as well as freshwater systems with a pH above 7.5.

How Ozone Works

Certain organic wastes are unable to be removed by conventional mechanical or biological filtration. Ozone oxidizes the water, breaking down these waste products. This makes the wastes easier to be processed by the filtration, resulting in clear water. Ozone also provides additional oxygen to the aquarium as well as killing bacteria and parasites by eating away at their cell membranes.

Ozonizers work by creating electrical discharges that combine oxygen molecules to form ozone molecules. The generated ozone is then added to an ozone reactor or protein skimmer in regulated amounts to diffuse into the aquarium water. Caution needs to be taken in adjusting the amount of ozone added to the water, as too much ozone can be hazardous to the fish as well as anyone nearby. 


Redox Potential (ORP)

ORP, or Oxidation Reduction Potential, is a measurement used to determine the oxidizing potential in water. In aquarium water, chemical reactions create a transfer of electrons that can be measured by a sensitive voltmeter to determine the ORP level. As ozone is introduced to the water, the ORP level gradually increases as the water gets sterilized. This ORP reading is used to further control the regulation of an ozonizer unit with a Redox controller, similar to how a thermostat controls the operation of a heater. When operating an ozone system, the ORP level should be 300-350 mV, which indicates an oxygen-rich environment with low waste levels. An ORP level higher than 350mV should be avoided, as it will create levels of ozone sterilization that could be hazardous to the aquarium inhabitants.

Setup and Operation

Deciding on the amount of ozone to add to your aquarium will depend on the volume of water, water and air flow, existing equipment, and the biological load in your system. In most cases, ozone production should be 5-15 mg/hour for every 25 gallons of water. Systems with fewer fish can be maintained with less than 5mg/hour per 25 gallons, while heavier bio loads with few invertebrates should be towards the 15mg/hour per 25 gallons. It is possible to dose in greater quantities of ozone for very heavy fish-only populations, however extreme caution will need to be taken. Due to the potential dangers of this, dosing above 15mg/hour per 25 gallons is normally not suggested.

The first step in adding ozone involves an air pump to force air into the ozonizer. An air drier is also used to reduce humidity and ensure ozone is generated in an efficient manner.

After the ozone is produced, it should never be directly diffused into the water. To help diffuse it in a safe, regulated manner, the ozone is run through a pressurized unit such as a protein skimmer or ozone reactor. Not only does this properly diffuse the ozone into the water, but the pressurized housing of the skimmer or reactor helps prevent excess ozone from escaping.

Since escaped ozone can be dangerous, it is necessary to install a carbon filter on your protein skimmer or ozone reactor at the areas where ozonized air escapes (I.E., the top of certain reactors or under the lid of the skimmer collection cup). It is also advisable to place an activated carbon filter at the outlet where the ozonized water enters back into the sump or aquarium. The ozone in the water then breaks down organics in the aquarium water and takes care of parasites and bacteria.

Ozonizers: More Powerful than a UV Sterilizer


UV sterilizers are commonly used in aquariums to control bacteria, algae, and parasites. However, when parasites are exposed to UV light, it is usually only intense enough to simply sterilize them to help prevent further reproduction. In contrast, ozonizers are able to take it a step further by outright killing parasites, doing a more effective job at controlling them.

Ozonizers are an excellent piece of equipment for the advanced aquarium owner looking to create the best possible water conditions for their inhabitants. With the increased oxygen and ability to break down organics, bacteria, and parasites, these systems work very well at improving the health of an aquarium.

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Karina May 23, 2011 at 10:58 pm

My name Karina from Jakarta, Indonesia.I am interested with ozonizer for seawater treatment.
I need it for my pilot project in culturing shrimp, with ozone production 1.5-2.0gram per hour.
Do you have suitable equipment for me and do you have any agent/distributor in Indonesia?

Thanks for your information


Ellen B. May 24, 2011 at 1:06 pm

Karina, thanks for checking out our site and leaving a comment! Our customer service team informed me that at this time we do not carry any of the actual ozonizers, we only have accessories for ozonizers. Sorry we cannot help you at this time.

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